Banding in images.

I attach 7 greyscale images. Each is a screengrab using the Jing app. One of a greyscale gradient, 3 of same gradient displayed in editors, and 3 of gradient saved from those editors

Note the banding in all images opened in graphics editors. Which explains why I'm finding it hard to create images without banding. Yet the base image - 'gradient - has little or no banding. This was viewed in the default Photos app that comes with Windows10.

If I simply open and save with no edits, image is fine. It's the display in-app that's banded.

Why is this happening.? I'm using a Radeon RX480 card on a Ryzen 7 1700 processor, through a Benq GW2765 monitor.